docs: add TodoMVC app to the ressources page

[bbaia]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[x] Other... Please describe: New sample to the ressources page

What is the current behavior?

Closes #

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for 051adf6 at https://previews.ngrx.io/pr2913-051adf6f/

[bbaia]

FYI, I've added new stuff to the repo :

On the component-store branch, you'll find a version based on component store (@ngrx/component-store).
Any feedback on the unit tests will be appreciated.

On the zoneless branch, you'll find a version working without Zone.js using @ngrx/component (Take a look to the latest commit of the branch).